Surgical manipulator for a telerobotic system

ABSTRACT

The invention is directed to manipulator assembly (2) for holding and manipulating a surgical instrument (14) in a telerobotic system. The assembly comprises a base (6) fixable by passive or power driven positioning devices to a surface, such as an operating table, and an instrument holder (4) movably mounted on the base. The instrument holder comprises a chassis (6) and an instrument support (70) movably mounted on the body and having an interface engageable with the surgical instrument to releasably mount the instrument to the instrument holder. A drive assembly (7) is operatively coupled to the instrument holder for providing the instrument with at least two degrees of freedom. The instrument holder is separable from the base and the drive assembly so that the holder can be sterilized. The assembly further includes a force sensing element (52) mounted distal to the holder and the drive assembly for detecting forces exerted on the surgical instrument and providing feedback to the surgeon. The assembly is attached to a remote center positioner (300) for constraining the instrument to rotate about a point coincident with the entry incision and an inclinometer (350) for preventing gravitational forces acting on the system&#39;s mechanisms from being felt by the surgeon.

This is a Continuation of U.S. patent application Ser. No. 08/487,020,filed Jun. 7, 1995, now abandoned, the disclosure of which isincorporated by reference.

BACKGROUND OF THE INVENTION

This invention relates to surgical manipulators and more particularly torobotically-assisted apparatus for use in surgery.

In standard laparoscopic surgery, a patient's abdomen is insufflatedwith gas, and trocar sleeves are passed through small (approximately 1/2inch) incisions to provide entry ports for laparoscopic surgicalinstruments. The laparoscopic surgical instruments generally include alaparoscope for viewing the surgical field, and working tools such asclamps, graspers, scissors, staplers, and needle holders. The workingtools are similar to those used in conventional (open) surgery, exceptthat the working end of each tool is separated from its handle by anapproximately 12-inch long extension tube. To perform surgicalprocedures, the surgeon passes instruments through the trocar sleevesand manipulates them inside the abdomen by sliding them in and outthrough the sleeves, rotating them in the sleeves, levering (i.e.,pivoting) the sleeves in the abdominal wall and actuating end effectorson the distal end of the instruments.

In robotically-assisted and telerobotic surgery (both open andendoscopic procedures), the position of the surgical instruments iscontrolled by servo motors rather than directly by hand or with fixedclamps. The servo motors follow the motions of a surgeon's hands ashe/she manipulates input control devices and views the operation via adisplayed image from a location that may be remote from the patient. Theservo motors are typically part of an electromechanical device orsurgical manipulator that supports and controls the surgical instrumentsthat have been introduced directly into an open surgical site or throughtrocar sleeves into a body cavity, such as the patient's abdomen. Duringthe operation, the surgical manipulator provides mechanical actuationand control of a variety of surgical instruments, such as tissuegraspers, needle drivers, etc, that each perform various functions forthe surgeon, i.e., holding or driving a needle, grasping a blood vesselor dissecting tissue.

This new method of performing telesurgery through remote manipulationwill create many new challenges. One such challenge is transmittingposition, force, and tactile sensations from the surgical instrumentback to the surgeon's hands as he/she operates the telerobotic system.Unlike other techniques of remote manipulation, telesurgery can give thesurgeon the feeling that he/she is manipulating the surgical instrumentsdirectly by hand. For example, when the instrument engages a tissuestructure or organ within the patient, the system should be capable ofdetecting the reaction force against the instrument and transmittingthis force to the input control devices. In this manner, the surgeon cansee the instrument contacting the tissue structure on the displayedimage and directly feel the pressure from this contact on the inputcontrol devices. Providing the appropriate feedback, however, can beproblematic because of other forces acting on the system, such asfriction within the telerobotic mechanisms, gravity and inertial forcesacting on the surgical manipulator or forces exerted on a trocar sleeveby the surgical incision.

In addition, to enable effective telesurgery, the manipulator must behighly responsive and must be able to accurately follow even the mostrapid hand motions that a surgeon frequently uses in performing surgicalprocedures. To achieve this rapid and responsive performance, atelerobotic servo system must be designed to have an appropriately highservo bandwidth which requires that the manipulator be designed to havelow inertia and to employ drive motors with relatively low ratio gear orpulley couplings.

Another challenge with telesurgery results from the fact that a portionof the electromechanical surgical manipulator will be in direct contactwith the surgical instruments, and will also be positioned adjacent theoperation site. Accordingly, the surgical manipulator may becomecontaminated during surgery and is typically disposed of or sterilizedbetween operations. Of course, from a cost perspective, it would bepreferable to sterilize the device. However, the servo motors, sensorsand electrical connections that are necessary to robotically control themotors typically cannot be sterilized using conventional methods, e.g.,steam, heat and pressure or chemicals, because they would be damaged ordestroyed in the sterilization process.

What is needed, therefore, is a robotically-assisted apparatus forholding and manipulating surgical instruments by remote control. Theapparatus should be configured for easy sterilization so that it can bereused after it has been contaminated during an operation. The apparatusshould be further capable of providing the surgeon with the appropriatefeedback from forces transmitted to and from the surgical instrumentduring the telerobotic operation and it should be configured tocompensate for gravitational forces acting on the apparatus so thatthese forces are not felt by the surgeon. In addition, the apparatusmust be highly responsive and must be able to accurately follow even themost rapid hand motions that a surgeon frequently uses in performingsurgical procedures.

SUMMARY OF THE INVENTION

According to the invention, an apparatus is provided for holding andmanipulating a surgical instrument during conventional open surgery orendoscopic procedures, such as laparoscopy. The apparatus comprises asupport base fixable by means of various passive or power drivenpositioning devices to a surface, such as an operating table, and aninstrument holder movably mounted on the base. The instrument holdercomprises a body and an instrument support movably coupled to the bodyand having an interface engageable with the surgical instrument toreleasably mount the instrument to the instrument holder. A driveassembly is operatively coupled to the instrument holder for providingthe instrument with at least two degrees of freedom. The drive assemblyincludes a first drive for moving the instrument support and a seconddrive for moving the instrument holder relative to the support base. Theapparatus includes means for removably coupling the instrument holderfrom the base and the drive assembly so that the holder can be separatedfrom the rest of the device and sterilized after a surgical procedure.

In a specific configuration, the support base includes a frame withdistal and proximal support members and a pair of shafts rotatablymounted within the support members. The instrument holder is slidablymounted on the support shafts for axial movement of the instrument. Inaddition, the shafts are each coupled to a drive motor for providing theinstrument with second and third degrees of freedom, e.g., rotation andend effector actuation. The drive motors are coupled to the proximalsupport member so that they will not be contaminated during surgery. Therotatable shafts can be removed by sliding them upward and out ofengagement with their lower bearings and the instrument holder so thatthe instrument holder can be easily removed from the support base forsterilization. The lower portion of the support base (including thedistal support member) may also be sterilized to decontaminate thoseparts that have contacted the instrument holder. In this manner, thesurgical manipulator can be easily sterilized after a surgical procedurewithout damaging the servo motors or the electrical connections requiredfor the telerobotic system.

The support base further comprises a sleeve, such as a cannula or trocarsleeve, mounted on the distal support member. The sleeve has an axialpassage for receiving the instrument therethrough and a force sensingelement mounted within the axial passage near the distal end of thesleeve. The force sensing element is configured to detect lateral forcesexerted on the element by the distal portion of the instrument duringsurgery. Since the force sensing element is mounted distal to theremainder of the apparatus, it is undisturbed by forces that may beexerted on the cannula by the surgical incision or by gravity andinertial forces that act on the instrument holder. When supported by apositioning device, the surgical manipulator can be used with aninclinometer to determine the true orientation of the instrument holderwith respect to the direction of the local gravitational field. Use ofthe inclinometer and force sensors with the manipulator facilitates thedesign of a telerobotic system in which the surgeon will directly sensethe forces acting against the end of the instrument, unaffected byextraneous forces acting on the telerobotic mechanism. In other words,the surgeon will feel as if his/her hands are holding the instrument atthe point in which the instrument contacts the force sensing element.

The invention is particularly useful for holding and manipulating asurgical instrument having an end effector, such as a pair of jaws,coupled to the distal end of the instrument shaft. To that end, theinstrument holder further includes an actuator driver having aninterface engageable with an end effector actuator on the instrument.The actuator driver includes a coupling that connects the driver to thedrive assembly for axially moving a portion of the driver relative tothe support base, thereby actuating the end effector of the instrument.In a preferred configuration, the coupling is a concentric helicalactuator that translates rotation from a drive motor into axial movementof the end effector actuator. Because of the symmetrical design of thehelical actuator, the actuation force applied by the drive motor willnot generate any effective side loads on the instrument, which avoidsfrictional coupling with other degrees of freedom such as axial movementand rotation of the instrument.

Other features and advantages of the invention will appear from thefollowing description in which the preferred embodiment has been setforth in detail in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial sectional elevational view of a robotic endoscopicsurgical instrument mounted to a manipulator assembly according to thepresent invention;

FIG. 1A is a partial sectional elevational view of the manipulatorassembly of FIG. 1 illustrating the removal of an instrument holder fromthe rest of the assembly;

FIGS. 2A and 2B are enlarged side and front cross-sectional views,respectively, of the surgical instrument of FIG. 1;

FIGS. 3A and 3B are perspective views of an instrument support and anactuator pin catch, respectively, for releasably mounting the surgicalinstrument to the manipulator assembly;

FIG. 4 is a front elevational view of the surgical instrument mountedwithin the instrument support and actuator pin catch of FIGS. 3A and 3B;

FIG. 5 is a front elevational view of an actuator driver for providingaxial movement of the actuator pin catch of FIG. 3B;

FIGS. 6A and 6B are enlarged cross-sectional views of an actuatorcarriage assembly and a helical actuator of the actuator driver of FIG.5;

FIG. 7 is an enlarged detail of a portion of the frame of themanipulator assembly of FIG. 1 illustrating a coupling mechanism forremoving the shafts from the frame;

FIG. 8 is a partial cross-sectional view of the instrument support ofFIG. 3A illustrating a locking mechanism for a twist lock interfaceaccording to the present invention; and

FIG. 9 is an elevational view of a remote center positioner for holdingthe manipulator assembly of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings in detail, wherein like numerals indicate likeelements, a manipulator assembly 2 is illustrated according to theprinciples of the invention. Manipulator assembly 2 generally includesan instrument holder 4 removably mounted to a base 6 and a driveassembly 7 for manipulating a surgical instrument 14 releasably coupledto instrument holder 4.

Referring to FIG. 1, base 6 comprises a frame 16 having proximal anddistal elongate support members 17, 19 and first and second ball-splineshafts 18, 20 rotatably coupled to support members 17, 19 via bearings22. Frame 16 further includes a support bracket 24 for attachingmanipulator assembly 2 to a remote center positioner 300, as discussedin more detail below (see FIG. 9). Drive assembly 7 comprises first,second and third drives 8, 10, 12, which are mounted to frame 16 andconfigured to provide three degrees of freedom to surgical instrument14. In the preferred embodiment, first drive 8 rotates instrument 14around its own axis, second drive 10 actuates an end effector 120 on thedistal end of instrument 14 and third drive 12 axially displacesinstrument 14 with respect to frame 16. Of course, it will be readilyrecognized by those skilled in the art that other configurations arepossible. For example, assembly 2 may include additional drives forproviding additional degrees of freedom to surgical instrument 14, suchas rotation and flexion of an instrument wrist.

First drive 8 comprises a rotation drive motor 26 fixed to frame 16 andcoupled to first shaft 18 by a drive belt 28 for rotating first shaft 18with respect to frame 16. Second drive 10 comprises a gripper drivemotor 30 fixed to frame 16 and coupled to second shaft 20 by a drivebelt 32 for rotating second shaft 20 with respect to frame 16. Thirddrive 12 comprises a vertical drive motor 34 coupled to instrumentholder 4 via a drive belt 36 and two pulleys 38 for axially displacinginstrument holder 4 with respect to frame 16. Drive motors 26, 30, 34are preferably coupled to a controller mechanism via servo-controlelectronics (not shown) to form a telerobotic system for operatingsurgical instrument 14 by remote control. The drive motors follow themotions of a surgeon's hands as he/she manipulates input control devicesat a location that may be remote from the patient. A suitabletelerobotic system for controlling the drive motors is described incommonly assigned co-pending application Ser. No. 07/823,932 filed Jan.21, 1992 TELEOPERATOR SYSTEM AND METHOD WITH TELEPRESENCE, which isincorporated herein by reference.

The above described telerobotic servo system preferably has a servobandwidth with a 3 dB cut off frequency of at least 10 hz so that thesystem can quickly and accurately respond to the rapid hand motions usedby the surgeon. To operate effectively with this system, instrumentholder 4 has a relatively low inertia and drive motors 26, 30, 34 haverelatively low ratio gear or pulley couplings.

In a specific embodiment, surgical instrument 14 is an endoscopicinstrument configured for introduction through a percutaneouspenetration into a body cavity, such as the abdominal or thoraciccavity. In this embodiment, manipulator assembly 2 supports a cannula 50on distal support member 19 of frame 16 for placement in the entryincision during an endoscopic surgical procedure (note that cannula 50is illustrated schematically in FIG. 1 and will typically be muchlonger). Cannula 50 is preferably a conventional gas sealing trocarsleeve adapted for laparoscopic surgery, such as colon resection andNissen fundoplication.

As shown in FIG. 1, cannula 50 preferably includes a force sensingelement 52, such as a strain gauge or force-sensing resistor, mounted toan annular bearing 54 within cannula 50. Bearing 54 supports instrument14 during surgery, allowing the instrument to rotate and move axiallythrough the central bore of bearing 54. Bearing 54 transmits lateralforces exerted by the instrument 14 to force sensing element 52, whichis operably connected to the controller mechanism for transmitting theseforces to the input control devices (not shown) held by the surgeon inthe telerobotic system. In this manner, forces acting on instrument 14can be detected without disturbances from forces acting on cannula 50,such as the tissue surrounding the surgical incision, or by gravity andinertial forces acting on manipulator assembly 2. This facilitates theuse of manipulator assembly in a robotic system because the surgeon willdirectly sense the forces acting against the end of instrument 14. Ofcourse, the gravitational forces acting on the distal end of instrument14 will also be detected by force sensing element 52. However, theseforces would also be sensed by the surgeon during direct manipulation ofthe instrument.

As shown in FIG. 1, instrument holder 4 comprises a chassis 60 mountedon shafts 18, 20 via ball-spline bearings 62, 64 so that chassis 60 maymove axially with respect to shafts 18, 20, but is prevented fromrotating with shafts 18, 20. Chassis 60 is preferably constructed of amaterial that will withstand exposure to high temperature sterilizationprocesses, such as stainless steel, so that chassis 60 can be sterilizedafter a surgical procedure. Chassis 60 includes a central cavity 66 forreceiving surgical instrument 14 and an arm 68 laterally extending fromchassis 60. Arm 68 is fixed to drive belt 36 so that rotation of drivebelt 36 moves instrument holder 4 in the axial direction along shafts18, 20.

Instrument holder 4 is removably coupled to base 6 and the drive motorsso that the entire holder 4 can be removed and sterilized byconventional methods, such as steam, heat and pressure, chemicals, etc.In the preferred configuration, arm 68 includes a toggle switch 69 thatcan be rotated to release arm 68 from drive belt 36 (FIG. 1). Inaddition, shafts 18, 20 are removably coupled to bearings 22 so that theshafts can be axially withdrawn from support members 17, 19 of frame 16,as shown in FIG. 1A. To this end, the distal bearings 22 preferablyinclude a coupling mechanism for allowing the removal of shafts 18, 20.As shown in FIG. 7, distal support member 19 includes a support collar71 within each distal bearing 22 having an inner bore 72 for passage ofone of the shafts 18, 20. Each support collar 71 has an internal groove73 and shafts 18, 20 each have an annular groove 74 (see FIG. 1A) neartheir lower ends that is aligned with internal grooves 73 when theshafts are suitably mounted within frame 16 (FIG. 1). A spring clip 75is positioned within each internal groove 73 to hold each shaft 18, 20within the respective support collar 71. Spring clip 74 has adiscontinuity (not shown) to allow removal of shafts 18, 20 upon theapplication of a threshold axial force on the shafts.

To remove instrument holder 4 from base 6, the operator rotates toggleswitch 69 to release arm 68 from drive belt 36 and removes drive belts28, 32 from drives 8, 10. As shown in FIG. 1A, the operator holdsinstrument holder 4 and pulls shafts 18, 20 upwards, providing enoughforce to release spring clips 75. Shafts 18, 20 will disengage fromdistal bearings 22 and slide through ball-spline bearings 62, 64 so thatinstrument holder 4 is disconnected from base 6. It should be understoodthat the invention is not limited to the above described means forremovably coupling instrument holder 4 to base 6 and drive assembly 7.For example, distal support member 19 may be removably coupled to therest of frame 16 so that the surgeon simply removes member 19 and slidesholder down and off shafts 18, 20. Proximal support member 17 may beremovably coupled to frame 16 in a similar manner. Alternatively, thedrive motors may be housed in a separate servo-box (not shown) that isremovably attached to base 6. In this configuration, the servo-box wouldbe removed from base 6 so that the entire base 6, together with holder4, can be sterilized.

The lower portion of base 6 (including distal support member 19) mayalso be sterilized to decontaminate those parts that come into contactwith holder 4 or instrument 14 (e.g., by dipping the lower portion ofbase 6 into a sterilizing bath). To facilitate this type ofsterilization, shafts 18, 20 will preferably be somewhat longer thanshown in FIG. 1 so that the upper portion of base 6, including driveassembly 7, is disposed sufficiently away from holder 4 and instrument14. In this manner, the surgical manipulator can be easily sterilizedafter a surgical procedure without damaging the drive motors or theelectrical connections required for the telerobotic system.

Instrument holder 4 further includes an instrument support 70 (seedetail in FIG. 3A), for releasably coupling surgical instrument 14 tothe manipulator assembly. Instrument support 70 is rotatably mountedwithin chassis 60 via mounting bearings 74 so that support 70 and theinstrument can be rotated therein. As shown in FIG. 1, support 70 iscircumscribed by an annular ring gear 76 having teeth that mesh with theteeth of a drive gear 78 mounted to first shaft 18. Drive gear 78 isconfigured around first shaft 18 such that it will rotate with firstshaft 18, thereby rotating instrument support 70 and the surgicalinstrument therewith. Drive gear 78 is also configured to move axiallywith respect to first shaft 18 to allow axial movement of instrumentholder 4 with respect to frame 16.

Instrument holder 4 further includes an actuator driver 80 (see detailin FIG. 5) movably mounted within axial guide slots 82 on either side ofchassis 60. Actuator driver 80 comprises a helical actuator 84 (seedetail in FIG. 6B) having a ring gear 86 that meshes with a gripperdrive gear 88 mounted to second shaft 20. Rotation of second shaft 20causes rotation of gripper drive gear 88, thereby rotating ring gear 86and helical actuator 84 within chassis 60. Actuator driver 80 furtherincludes an actuator carriage assembly 90 (see detail in FIG. 6A) forreleasably coupling an end effector actuator of surgical instrument 14to instrument holder 4 (see FIG. 2). carriage assembly 90 is mountedwithin helical actuator 84 and chassis 60 such that rotation of helicalactuator 84 causes a corresponding axial movement of carriage assembly90 with respect to chassis 60, as discussed in greater detail below.

FIGS. 2A and 2B illustrate a specific embodiment of an endoscopicsurgical instrument 14 capable of being operated by a motorizedmanipulator, such as manipulator assembly 2, for telerobotic surgery.Surgical instrument 14 can be a variety of conventional endoscopicinstruments adapted for delivery through a percutaneous penetration intoa body cavity, such as tissue graspers, needle drivers, microscissors,electrocautery dissectors, etc. In the preferred embodiment, instrument14 is a tissue grasper comprising a shaft 100 having a proximal end 102,a distal end 104 and a longitudinal axis 106 therebetween. A knurledhandle 114 is attached to proximal end 102 of shaft 100 to facilitatemanipulation of instrument 14.

Shaft 100 is preferably a stainless steel tube having an outer diameterin the range of 2-10 mm, usually 4-8 mm, so as to fit within a cannulahaving an internal diameter in the range of 2-15 mm. Shaft 100 can alsobe introduced directly through a percutaneous incision in the patient.Shaft 100 has a length selected to reach a target site in a body cavity,such as the abdomen, and to extend sufficiently out of the body cavityto facilitate easy manipulation of surgical instrument 14. Thus, shaft100 should be at least between 10 cm and 40 cm and is preferably between17 cm and 30 cm. It should be noted that although shaft 100 is shown ashaving a circular cross-sectional shape in the drawings, shaft 100 couldalternatively have a rectangular, triangular, oval or channelcross-sectional shape.

In a specific configuration, shaft 100 includes a mounting means forreleasably coupling surgical instrument 14 to instrument support 70 andfirst drive 8 of manipulator assembly 2. In the preferred embodiment,mounting means comprises a pair of opposed mounting pins 116 extendinglaterally outward from shaft 100. Mounting pins 116 are rigidlyconnected to shaft 100 and are adapted for engaging a twist-lockinterface on instrument support 70, as discussed in detail below. Itshould be understood that the invention is not limited to a pair ofopposing pins and mounting means can include a single mounting pin or aplurality of pins extending circumferentially around shaft.Alternatively, pins 116 may have a variety of other shapes, such asspherical or annular, if desired.

Instrument 14 includes an end effector 120 extending from distal end 104for engaging a tissue structure on the patient, such as the abdomenduring laparoscopic surgery. In the preferred embodiment, end effector120 comprises a pair of jaws 122, 124 that are movable between open andclosed positions for grasping a blood vessel, holding a suture, etc.Jaws 122, 124 preferably have transverse grooves or other texturalfeatures (not shown) on opposing surfaces to facilitate gripping of thetissue structure. To avoid the possibility of damaging the tissue towhich jaws 122, 124 are applied, the jaws may also include atraumaticmeans (not shown), such as elastomeric sleeves made of rubber, foam orsurgical gauze wrapped around jaws 122, 124.

To move jaws 122, 124 between the open and closed positions, instrument14 includes an end effector actuator releasably coupled to actuatordriver 80 and second drive 10 of manipulation assembly 2 (see FIG. 4).In the preferred embodiment, end effector actuator comprises a pair ofopposed actuator pins 132 laterally protruding from axially extendingslots 134 in shaft 100. Actuator pins 132 are coupled to an elongate rod136 slidably disposed within an inner lumen 138 of shaft 100. Actuatorpins 132 are slidable within slots 134 so that rod 136 is axiallymovable with respect to shaft 100 and mounting pins 116 to open andclose jaws 122, 124, as is conventional in the art. Elongate rod 136 hasa proximal portion 140 that is disposed within an inner lumen 142 withinshaft 100 to prevent actuator pins 132 from moving in the lateraldirection and to ensure that rod 136 remains generally centered withinshaft 100 during a surgical procedure.

Jaws 122, 124 are preferably biased into the closed positioned by anannular compression spring 144 positioned within shaft 100 betweenactuator pins 132 and an annular disc 146 fixed to the inside surface ofshaft 100. During endoscopic procedures, this allows the surgical teamto introduce jaws 122, 124 through cannula 50 (or any other type ofpercutaneous penetration) and into the body cavity without getting stuckwithin cannula 50 or damaging surrounding tissue.

FIGS. 3A, 3B and 4 illustrate a twist lock mechanism for releasablyconnecting surgical instrument 14 to manipulator assembly 2 so thatdifferent instruments may be rapidly changed during an endoscopicsurgical procedure. As shown in FIG. 3A, instrument support 70 comprisesan annular collar 200 defining a central bore 202 for receiving shaft100 of surgical instrument 14. Collar 200 further defines an axiallyextending slot 204 in communication with bore 202 and sized to allowmounting and actuator pins 116, 132 of instrument 14 to slidetherethrough (see FIG. 4). Two locking slots 206 are cut into annularcollar 200 at a transverse angle, preferably about 900, to axiallyextending slot 204 (note that only one of the locking slots are shown inFIG. 3A). Locking slots 206 intersect slot 204 near the center ofannular collar 200 and extend circumferentially around bore 202,preferably about 900, to allow rotation of both mounting pins 116therethrough, as discussed below.

As shown in FIGS. 3A and 8, instrument support 70 further comprisesmeans for locking mounting pins 116 into locking slots 206 so that theinstrument cannot be accidently twisted and thereby disengaged frominstrument support 70 during surgery. Preferably, the locking meanscomprises a latch assembly having a plunger 210 slidably disposed withina hole 212 in collar 200, as shown in FIG. 3A. Plunger 210 comprises anL-shaped latch 213 coupled to a release button 214 by a rod 215extending through hole 212. Plunger 210 is movable between a firstposition, where latch 213 is not disposed within locking slots 206 sothat mounting pins 116 are free to rotate therethrough, and a secondposition, where latch 213 is at least partially disposed within one ofthe locking slots 206 so as to prevent rotation of mounting pins 116.Latch 213 is preferably biased into the second or locked position by acompression spring 216.

Button 214 is disposed on the upper surface of support 70 for manualactuation by the surgeon or automatic actuation by base 6. Preferably,when instrument holder 4 is moved to its most proximal position (seeFIG. 1), proximal support member 17 of frame 16 depresses release switch214 to move latch 213 into the first or open position. With thisconfiguration, instruments can be exchanged only when the instrumentholder 4 is in the most proximal position, where shaft 100 of instrument14 is easily accessible. In addition, this prevents the accidentalrelease of the instrument when its distal end has penetrated cannula 50and is disposed within the body cavity.

The intersecting axial and locking slots 204, 206 form an interface forreleasably coupling mounting pins 116 of surgical instrument 14 toinstrument holder 4. To insert instrument 14, the surgeon alignsmounting pins 116 with axial slot 204 and slides the instrument throughbore 202 of annular collar 200 until mounting pins 116 are aligned withlocking slots 206, as shown in FIG. 4. The instrument is then rotated asufficient distance, preferably about a 1/4 turn, through locking slots206 so that the pins are no longer aligned with axial slot 204. Wheninstrument 14 is moved distally, switch 214 is released (FIG. 1) andlatch 213 moves into locking slots 206 to prevent mounting pins 116 fromrotating back into alignment with axial slot 204 so that instrument 14is secured to instrument support 70. It should be noted that a singlemounting pin may be utilized with the above described configuration tolock the surgical instrument to the support. However, two opposing pinsare preferred because this configuration reduces torsional forces on theinner surface of locking slots 206.

As shown in FIG. 8, the locking means preferably includes a ball detent217 disposed within collar 200. Ball detent 217 is biased upward intoone of the locking slots 206 by a spring 218. Ball detent 217 serves totemporarily capture mounting pins 116 in a position rotated about 90°from alignment with axial slot 204. This ensures that the mounting pinswill be completely rotated into the proper position (i.e., out of theway of latch 213) when instrument 14 is twisted into instrument holder.Otherwise, when switch 214 is released, latch 213 could become engagedwith mounting pins 216 so that the latch is unable to move completelyinto the locked position, thereby potentially causing the accidentalrelease of instrument 14 during surgery.

As shown in FIGS. 3B, 4 and 5, actuator driver 80 of instrument holder 4further comprises an actuator pin catch 220 for releasably holding andmoving actuator pins 132 of instrument 14. Actuator pin catch 220 isconstructed similarly to instrument support 70 (FIG. 3A), comprising anannular collar 222 that defines a bore 224 for receiving shaft 100 andan axially extending slot 226 for receiving actuator pins 132. A lockingslot 228 is cut into actuator pin catch 220 at a 90° angle so thatactuator pins can be rotated into the lock slot to couple actuator pins132 to actuator driver 66, as discussed above in reference to themounting pins. It should be noted that slot 226 need not extendcompletely through collar 222 since actuator pins 132 are locateddistally of mounting pins 116 (the instrument is preferably insertedjaws first). Of course, actuator and mounting pins 132, 116 may bereversed so that the mounting pins are distal to the actuator pins, ifdesired.

Referring to FIG. 6A, actuator pin catch 220 is rotatably mounted on aball bearing 230 in actuator carriage assembly 90. Bearing 230 allowsthe pin catch 220 to rotate freely in carriage assembly 90 whilepreventing relative axial motion. Therefore, when instrument 14 isrotated by first drive 8, actuator pins 132 will rotate within carriageassembly 90. Carriage assembly 90 further comprises two sets of axles232 for rotatably supporting a pair of inner rollers 236 and a pair ofouter rollers 238. As shown in FIG. 1, outer rollers 238 are slidablydisposed within axial guide slots 82 of chassis 60 to prevent rotationof carriage assembly 90 with respect to chassis 60. Inner and outerrollers 236, 238 cooperate with helical actuator 84 and chassis 60 ofinstrument holder 4 to move axially with respect to the holder, therebyaxially moving pin catch 220 and actuator pins 132 therewith relative toshaft 100 of instrument 14 (which actuates jaws 122, 124, as discussedabove).

As shown in FIG. 6B, helical actuator 84 includes a central bore 240 forreceiving carriage assembly 90 and surgical instrument 14 and twoopposing helical tracks 242, 244 each extending circumferentially aroundhelical actuator 84 (preferably slightly less than 180°) for receivinginner rollers 236 of carriage assembly 90, as shown in FIG. 5. Withouter rollers 238 constrained in axial guide slots 82 of chassis 60,rotation of helical actuator 84 causes carriage assembly 90 (andactuator pin catch 220) to move up or down, depending on the sense ofthe rotation. Because of the symmetrical design of helical actuator 84,the actuation force applied by second driver 10 will not generate anyeffective side loads on instrument 14, which avoids frictional couplingwith other degrees of freedom such as axial (third driver 12) androtation (first driver 8). In the preferred embodiment, helical tracks242, 244 have a pitch selected such that the mechanism can be easilyback-driven, allowing grip forces to be sensed in a position-servoedteleoperation system.

As shown in FIGS. 3A and 3B, instrument holder 4 further includes a pairof axial guide pins 250, 252 fixed to instrument support 70. Actuatorpin catch 220 has a pair of openings 254, 256 for receiving guide pins250, 252. Guide pins 250, 252 prevent relative rotation between pincatch 220 and support 70 (so that actuator and mounting pins 116, 132can both rotate with the instrument) and allow axial movement relativeto each other (so that end effector 120 can be actuated by axialmovement of actuator pins 132).

FIG. 9 is an elevational view of a remote center positioner 300 whichcan be used to support manipulator assembly 2 above the patient (notethat support manipulator 2 is not shown in FIG. 8). Remote centerpositioner 300 provides two degrees of freedom for positioningmanipulator assembly 2, constraining it to rotate about a point 308coincident with the entry incision. Preferably, point 308 will beapproximately the center of bearing 54 in cannula 50 (FIG. 1). A morecomplete description of remote center positioner 300 is described incommonly assigned co-pending application Ser. No. 08/062,404 filed May14, 1993 REMOTE CENTER POSITIONER now abandoned, which is incorporatedherein by reference.

A first linkage means is indicated generally by the numeral 321 and asecond linkage in the form of a parallelogram is indicated by thenumeral 323. The first linkage means is pivotally mounted on a baseplate for rotation about an x--x axis. The second linkage means ispivotally connected to the first linkage means and is adapted to move ina plane parallel to the first linkage. Five link members (includingextensions thereof), 311, 312, 313, 314, and 315 are connected togetherwith pivot joints 316-320. A portion of element 313 extends beyond pivot320 of the parallelogram linkage. The parallelogram linkage has anoperating end at link member 313 and a driving end at link member 312.The elongated element 313 may, as desired later, carry a surgicalinstrument or other device, such as support bracket 24 of manipulatorassembly 2. The pivot joints allow relative motion of the link membersonly in the plane containing them.

A parallelogram linkage is formed by corresponding link members 314, 315and link members 312 and 313. The portions of link members 314 and 315of the parallelogram are of equal length as are the portions of members312 and 313 of the parallelogram. These members are connected togetherin a parallelogram for relative movement only in the plane formed by themembers. A rotatable joint generally indicated by the numeral 322 isconnected to a suitable base 324. The rotatable joint 322 is mounted ona base plate 326 adapted to be fixedly mounted to the base support means324. A pivot plate 328 is pivotally mounted to base plate 326 bysuitable means at, such as, pivots 330, 332. Thus pivot plate 328 may berotated about axis x--x through a desired angle Θ2. This may beaccomplished manually or by a suitable pivot drive motor 334.

A first linkage is pivotally mounted on the pivot plate 328 of therotatable joint 322. The linkage elements 311, 312 and the link membersare relatively stiff or inflexible so that they may adequately supportan instrument used in surgical operations. Rods made of aluminum orother metal are useful as such links. The linkage elements 311 and 312are pivotally mounted on base plate 328 for rotation with respect to therotatable joint by pivots 336 and 338. At least one of the pivots 336,338 is positioned so that its axis of rotation is normal to andintersects the x--x axis. Movement may occur manually or may occur usinga linkage drive motor 340. The first linkage is also shaped in the formof a parallelogram formed by linkage elements 311, and 312; the portionof link member 315 connected thereto by pivots 316, 318; and base plate328. One of the link members 315 is thus utilized in both the first 321and second 323 linkage means. Linkage element 312 also forms a commonlink of both the first linkage means 321 and the second linkage means323. In accordance with the invention, a remote center of sphericalrotation 308 is provided by the above described embodiment of apparatuswhen the linkage element 311 is rotated and/or when pivot plate 328 isrotated about axis x--x. Thus, the end of element 313 can be movedthrough desired angles Θ1 and Θ2 or rotated about its own axis while theremote center of rotation remains at the same location.

FIG. 9 also shows an inclinometer (not shown) attached to the base ofremote center positioner 300. The remote center positioner may bemounted at an arbitrary orientation with respect to vertical dependingon the particular surgery to be performed, and inclinometer (not shown)can be used to measure this orientation. The measured orientation can beused to calculate and implement servo control signals necessary tocontrol the telerobotic system so as to prevent gravitational forcesacting on the system mechanisms from being felt by the surgeon.

Variations and changes may be made by others without departing from thespirit of the present invention. For example, it should be understoodthat the present invention is not limited to endoscopic surgery. Infact, instrument holder 4, along with a telerobotic control mechanism,would be particularly useful during open surgical procedures, allowing asurgeon to perform an operation from a remote location, such as adifferent room or a completely different hospital.

What is claimed is:
 1. An apparatus for manipulating a surgicalinstrument in a sterile surgical field comprising:a support base fixableto a surface; a sterilizable instrument holder movably mounted on saidsupport base and adapted to releasably hold the surgical instrument, theinstrument holder comprising: a body; and an instrument support movablymounted on said body and having an interface engageable with thesurgical instrument to releasably mount the instrument to saidinstrument holder; a drive assembly operatively coupled to saidinstrument holder for providing said instrument with at least twodegrees of freedom, said drive assembly comprising:a first controllablemotor operatively connected to move said instrument support; and asecond controllable motor operatively connected to move said instrumentholder body relative to said support base; a coupling mechanism forremovably attaching said instrument holder to said support base and saiddrive assembly, wherein said instrument holder is separable from saidsupport base and said drive assembly for sterilization of saidinstrument holder between surgical procedures; wherein said support basecomprises first and second spaced support shafts and said instrumentholder comprises first. and second mounts slidably mounted to the firstand second support shafts; wherein said instrument holder body furtherincludes an arm removably coupled to said second controllable motor foraxial movement of said first and second mounts along said first andsecond support shafts thereby moving said instrument in an axial,direction; wherein said support base comprises a frame having distal andproximal elongate support members, said first and second shafts eachhaving first and second ends rotatably supported within said distal andproximal support members; wherein said coupling mechanism comprises adisconnecting means for separating said spaced support shafts from saidsupport base to allow said instrument holder to be removed from saidsupport base and said drive assembly; and wherein said disconnectingmeans comprises an annular groove in each of the spaced support shaftsand an internal grove in each of said mounts in communication with saidannular groove, said disconnecting means further including a spring clippositioned within said annular and internal grooves so to prevent axialmovement of said shafts relative to said mounts, said spring clip havingan opening for allowing release of said shafts from said mounts when athreshold axial forces is applied to said shafts.
 2. An instrumentholder adapted to be driven by a drive assembly coupled to a roboticcontrol mechanism for manipulation of a surgical instrument of the typehaving a shaft with an axially fixed mounting means, an end effector anda movable end effector actuator, the instrument holder comprising:a bodyhaving an axial passage for receiving said instrument and at least onemount for movably coupling said body to the drive assembly; aninstrument support having an axial passage for receiving said instrumentand a first interface engageable with the axially fixed mounting meansof the instrument for releasably mounting the instrument to saidinstrument holder, said instrument support being rotatably coupled tosaid body and having a first coupling structured and arranged to connectsaid instrument support to the drive assembly for rotating saidinstrument; an actuator driver having an axial passage for receivingsaid instrument, a second interface engageable with the end effectoractuator of the instrument and a second coupling for connecting saidactuator driver to the drive assembly, said actuator driver furthercomprising means for translating rotational movement of the secondcoupling into axial displacement of the second interface relative tosaid body to actuate the end effector of the instrument.
 3. The holderof claim 2 wherein said translating means comprises a first portionrotatably mounted to said body and a second portion axially movable withrespect to said body, said first portion being coupled to said secondportion such that rotation of said first portion causes axialdisplacement of said second portion and the second interface therewith.4. The holder of claim 3 wherein said second coupling is an annular gearmember structured and arranged for coupling to a motor shaft forrotation of said first portion of said actuator driver.
 5. The holder ofclaim 3 wherein said second portion of said actuator driver comprises acarriage assembly movably mounted to said body and an annular collarreleasably coupled to said end effector actuator of said instrument androtatably coupled to said actuator carriage assembly.
 6. The holder ofclaim 5 wherein said body includes opposing axial slots, said carriageassembly including a first pair of rotatable members disposed withinsaid axial slots to prevent rotation of said actuator carriage assemblywith respect to said instrument holder and to allow axial movement withrespect to said holder.
 7. The holder of claim 6 wherein said carriageassembly further includes a second pair of rotatable members disposedradially inward from said first pair of rotatable members, said firstportion of said actuator driver comprising a concentric helical actuatorwith a pair of helical slots for receiving said second pair of rotatablemembers so that rotation of said helical actuator axially displaces saidcarriage assembly and said annular collar with respect to saidinstrument holder.
 8. The holder of claim 2 wherein said first couplingcomprises an annular gear member structured and arranged for coupling toa motor shaft for rotation of said instrument support.